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A HYBRID MODEL FOR SIMULATING VELOCITY FIELD OF A RIVER WITH COMPLEX GEOMETRY PLUNGED BY multiple jets

Journal of Hydrodynamics 2006年第6期18卷 752-759页

作者： LI Lian-xia LIAO Hua-sheng LI Tian-xiang State Key Laboratory of Hydraulics and Mountain River Engineering Sichuan University Chengdu 610065China

A hybrid model that combines both physical and numerical models was employed to simulate the velocity field in a river area in complex geometry with multiple plunging jets. The simulation was based on experiments concerning energy dissipation and scour prevention at the Xiluodu Hydropower Station on the Yangtze River. The calculated results indicate that the complex geometry of the river area has a significant influence on the velocity field, especially on the circulation flow pattern at upstream and downstream of the plunging area and on the asymmetric characteristics of the spiral flow near both banks. The scour characteristics of the downstream river bed caused by the multiple jets were also predicted and analyzed according to the characteristics of the calculated velocity field. The good agreement between the simulated and experimental results indicates that the hybrid model can be used to effectively solve complicated 3-D problems with complex geometric and inlet conditions. Such problems may not easily be solved by using either a physical or a numerical model alone, and therefore the method presented in this article is considered to be a practical and effective way of dealing with this kind of problems.

关键词： hybrid models turbulence model scour multiple jets

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Study on the flow field and concentration characteristics of the multiple tandem jets in crossflow

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Science China(Technological Sciences) 2012年第12期55卷 2778-2788页

作者： LI ZhiWei HUAI WenXin QIAN ZhongDong State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan UniversityWuhan 430072China

The characteristics of single and multiple tandem jets(n=2,3,4) in crossflow have been investigated using the realizable k-ε *** results of this model agree well with experimental measurements using PIV(Particle Image Velocimetry) or LIF(Laser Induced Fluorescence).We analyzed the calculated results and obtained detailed properties of velocity and concentration of the multiple jets in the pre-merging and post-merging *** the velocity ratio is identical,the bending degree of the leading jet is greater than that of the rear *** last jet penetrates deeper as the jet number increases,and the shielding effect of the front jet declines with jet spacing *** of the jet and crossflow induces formation and development of a counter-rotating vortex pair(CVP).CVP makes the distribution of concentration appear kidney-shaped(except in the merging region),and maximum concentration is at the center of the counter-rotating *** at the CVP center is 1.03-1.4 times that of the local jet ***-merging velocity and concentration characteristics differ from those of the single jet because of the shielding effect and mixing of all *** paper presents a unified formula of trajectory,concentration half-width and trajectory dilution,by introducing a reduction factor.

关键词： multiple jets dilution trajectory concentration half-width counter-rotating vortex pair(CVP)

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Numerical Optimization of Pressure Force from multiple jets Impinging on a Moving Curved Surface for Industrial Drying Machines

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Open Journal of Fluid Dynamics 2021年第4期11卷 192-209页

作者： Ali Chitsazan Georg Klepp Mohammad Esmaeil Chitsazan Birgit Glasmacher Institute for Energy Research Ostwestfalen-Lippe University of Applied Sciences and Arts Lemgo Germany Research Institute of Education Ahvaz Iran Institute for Multiphase Processes Leibniz University Hannover Hannover Germany

Jet force on the surface is typical for impinging jets towards the surface and it is very important in drying applications for force-sensitive surfaces. The designer should optimize the design parameters of industrial drying equipment to achieve minimum pressure force between multiple jets and a moving curved surface. SST k-ω turbulence model is used to simulate a real geometry for industrial drying applications. The SST k-ω turbulence model succeeded with reasonable accuracy in reproducing the experimental results. The jet to surface distance, jet to jet spacing, jet inlet velocity, jet angle, and surface velocity are chosen as the design parameters. For the optimization of the impinging round jet, the pressure force coefficient on the moving curved surface is set as the objective function to be minimized. The SHERPA search algorithm is used to search for the optimal point from the weighted sum of all objectives method. One correlation is developed and validated for the pressure force coefficient. It is found that the pressure force coefficient is highly dependent on the nozzle to surface distance and jet angle but relatively insensitive to jet inlet velocity, jet to jet spacing, and surface velocity. The minimum pressure force coefficient correlates with a high value of nozzle to surface distance (tenfold diameter in this analysis) and a low value of the jet angle (40? in this analysis). The agreement in the prediction of the pressure force coefficient between the numerical simulation and developed correlation is found to be reasonable and all the data points deviate from the correlation approximately 8% on average.

关键词： multiple jets Pressure Force Surface Motion Surface Curvature CFD Optimization

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Numerical Investigation on Turbulent multiple jets Merging and Acoustic Characteristic in the Slab Scarfing Process

Numerical Investigation on Turbulent Multiple Jets Merging a...

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第十届中国钢铁年会暨第六届宝钢学术年会

作者： Li Yiming Qi Fengsheng Wang Xichun Li Baokuan School of Materials and Metallurgy Northeastern University

In order to predict the multiple jets screech phenomenon in the scarfing process of rolling slab, a three-dimensional transient mathematical model has been developed to investigate the turbulent multiple jets merging. Large eddy simulation（LES） with dynamic Smagorinsky sub-grid scale（SGS） approach was applied to simulate the turbulent multi-jet flow field. The acoustic field was calculated by the Ffowcs Williams-Hawkings（FW-H） integral equation. In consideration of the compressibility of high Mach number gas jets, density-based explicit formulation was adopted to solve the coupled system of governing equations, and the viscosity was approximated by Sutherland kinetic theory. The multiple jets merging acoustic characteristic was demonstrated, as well as the noise intensity were predicted with a good accuracy of practical data. The results indicated that multiple jets merging phenomenon is induced by the Coanda effect, and adding to the complexity and instability of flow field. The main factors affecting multiple jets merging are injection orifice diameter and distances between orifices. The overall sound pressure level（OASPL） profiles have a directive property, which is also influenced by the multiple jets merging. Controlling multiple jets turbulent intensity and taking advantage of the noise directionality are both good measures for noise reduction. The conclusion obtained in this study can provide valuable data to guide the development of manufacturing-green technology in the scarfing process.

关键词： multiple jets acoustic characteristic noise predicted coanda effect scarfing process

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Three-Di mensional Computations of multiple Tandemjets in Crossflow

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China Ocean Engineering 2006年第1期20卷 99-112页

作者：肖洋李行伟唐洪武 YUDae-Young College of Water Conservancy and Hydropower Engineering Hohai UniversityNanjing 210098China Department of Civil Engineering The University of Hong KongHong Kong China

The mixing and merging characteristics of multiple tandem jets in crossflow are investigated by use of the Computational Fluid Dynamics （CFD） code FI,UENT. The realizable k - ε model is employed for turbulent elosure of the Reynolds-averaged Navier-Stokes equations. Numerical experiments are performed for 1-, 2- and 4-jet groups, tbr jet-tocrossflow velocity ratios of R = 4.2 ～ 16.3. The computed velocity and scalar concentration field are in good agreement with experiments using Particle Image Velocimetry （PIV） and Laser Induced Fluorescence （LIF）, as well as previous work. The results show that the leading jet behavior is similar to a single free jet in crossflow, while all the downstream rear jets have less bent-over jet trajectories - suggesting a reduced ambient velocity for the rear jets. The concentration decay of the leading jet is greater than that of the rear jets. When normalized by appropriate crossflow momentum length scales, all jet trajectories follow a universal relation regardless of the sequential order of jet position and the nund）er of jets. Supported by the velocity and trajectory measurements, the averaged maximum effective crossflow velocity ratio is computed to be in the range of 0.39 to 0.47.

关键词： jet in crossflow multiple jets realizable turbulence model mixing and transport computational fluid dynamics

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